Diclofenac sodium which is a non-steroidal drug, has an excellent anti-inflammatory analgesic, antipyretic effect as in Indomethacin and the utility thereof is highly evaluated. Therefore, diclofenac sodium is widely used as a tablet or a suppository in a clinical field.
Diclofenac sodium, however, has a disadvantage to cause various side effects such as gastro-intestinal lesion when orally administered. In order to minimize such side effects, attempts are made to administer diclofenac sodium in an enteric tablet or as a suppository. However, the use thereof is restricted for patients having the gastrointestinal lesion.
Recently, in order to overcome the above problems, various ointments and adhesive preparations containing diclofenac sodium as an effective component have been developed. They are expected to exhibit excellent local action and to prevent the side effects such as the gastro-intestinal lesion by applying to an inflammatory site so as to percutaneously absorb the effective component.
However, the skin has a stratum corneum containing keratin as a main component and contains a large amount of a fat-soluble component such as fat, wax and cholesterol. Therefore, the skin has a physiological defensive function, a so-called "barrier function", and as a result, it is difficult to easily make a percutaneous absorption of the drug. Against drugs having a salt form, such as diclofenac sodium, the skin exhibits a strong barrier function.
The other side, the skin adhesive preparations are comprised of rubber or acrylic high molecular weight material as a base material. These materials generally do not dissolve drugs sufficiently, and it is quite difficult to uniformly dissolve the drug having the salt form such as diclofenac sodium and maintain the dissolved state. Even if the drug in the skin adhesive preparation is prepared in the dissolved state, crystallization of the drug contained occurs during storage, sometimes inhibiting the percutaneous absorption of the drug.